diff --git a/doc/sigma_doc.doc b/doc/sigma_doc.doc
new file mode 100644
index 00000000..40f24e77
Binary files /dev/null and b/doc/sigma_doc.doc differ
diff --git a/sigma/sigma_cis.c b/sigma/sigma_cis.c
index 112bc4ed..623e163b 100644
--- a/sigma/sigma_cis.c
+++ b/sigma/sigma_cis.c
@@ -1,6 +1,6 @@
 /* sigma_cis.c: Sigma decimal instructions
 
-   Copyright (c) 2007-2008, Robert M Supnik
+   Copyright (c) 2007-2018, Robert M Supnik
 
    Permission is hereby granted, free of charge, to any person obtaining a
    copy of this software and associated documentation files (the "Software"),
@@ -26,6 +26,8 @@
    Questions:
 
    1. On the Sigma 9, in ASCII mode, is an ASCII blank used in EBS?
+
+   02-Jun-2018  RMS     Fixed unsigned < 0 in decimal compare (Mark Pizzolato)
 */
 
 #include "sigma_defs.h"
@@ -100,7 +102,7 @@ uint32 cis_dec (uint32 op, uint32 lnt, uint32 bva)
 {
 dstr_t src1, src2, src2x, dst;
 uint32 i, t, kint, ldivr, ldivd, ad, c, d, end;
-int32 sc;
+int32 sc, scmp;
 uint32 tr;
 
 if (lnt == 0)                                           /* adjust length */
@@ -163,10 +165,10 @@ switch (op) {                                           /* case on opcode */
         if (src1.sign ^ src2.sign)                      /* signs differ? */
             CC = src1.sign? CC4: CC3;                   /* set < or > */
         else {                                          /* same signs */
-            int32 t = CmpDstr (&src1, &src2);           /* compare strings */
-            if (t < 0)
+            scmp = CmpDstr (&src1, &src2);              /* compare strings */
+            if (scmp < 0)
                 CC = (src1.sign? CC3: CC4);
-            else if (t > 0)
+            else if (scmp > 0)
                 CC = (src1.sign? CC4: CC3);
             else CC = 0;
             }
@@ -720,11 +722,11 @@ return cy;
 void SubDstr (dstr_t *s1, dstr_t *s2, dstr_t *ds)
 {
 uint32 i;
-dstr_t Compl;
+dstr_t complm;
 
 for (i = 0; i < DSTRLNT; i++)                           /* 9's comp s2 */
-    Compl.val[i] = 0x99999999 - s1->val[i];
-AddDstr (&Compl, s2, ds, 1);                            /* s1 + ~s2 + 1 */
+    complm.val[i] = 0x99999999 - s1->val[i];
+AddDstr (&complm, s2, ds, 1);                           /* s1 + ~s2 + 1 */
 return;
 }
 
diff --git a/sigma/sigma_cpu.c b/sigma/sigma_cpu.c
index 2ba09efa..87903d96 100644
--- a/sigma/sigma_cpu.c
+++ b/sigma/sigma_cpu.c
@@ -248,7 +248,7 @@ extern uint32 io_tio (uint32 rn, uint32 bva);
 extern uint32 io_tdv (uint32 rn, uint32 bva);
 extern uint32 io_hio (uint32 rn, uint32 bva);
 extern uint32 io_aio (uint32 rn, uint32 bva);
-extern t_stat int_reset (DEVICE *dev);
+extern uint32 int_reset (DEVICE *dev);
 extern void io_set_eimax (uint32 lnt);
 extern void io_sclr_req (uint32 inum, uint32 val);
 extern void io_sclr_arm (uint32 inum, uint32 val);
@@ -476,7 +476,6 @@ while (reason == 0) {                                   /* loop until stop */
         if (sim_brk_summ &&
             sim_brk_test (PC, SWMASK ('E'))) {          /* breakpoint? */
             reason = STOP_IBKPT;                        /* stop simulation */
-            sim_interval++;                             /* don't count non-executed instruction */
             break;
             }
         if (PSW_QRX9 && (PC & PSW1_XA))                 /* S9 real ext && ext? */
@@ -1124,7 +1123,7 @@ switch (op) {
         res = R[rn] | opnd;
         CC34_W (res);                                   /* set CC's */
         R[rn] = res;                                    /* store */
-        break;
+    break;
 
     case OP_EOR:                                        /* xor */
         if ((tr = Ea (IR, &bva, VR, WD)) != 0)          /* get eff addr */
@@ -1134,7 +1133,7 @@ switch (op) {
         res = R[rn] ^ opnd;
         CC34_W (res);                                   /* set CC's */
         R[rn] = res;                                    /* store */
-        break;
+    break;
 
 /* Compares */
 
@@ -2705,7 +2704,7 @@ return SCPE_OK;
 t_stat cpu_show_addr (FILE *of, UNIT *uptr, int32 val, CONST void *desc)
 {
 t_stat r;
-CONST char *cptr = (CONST char *) desc;
+char *cptr = (char *) desc;
 uint32 ad, bpa, dlnt, virt;
 static const char *lnt_str[] = {
     "byte",
@@ -2825,7 +2824,7 @@ t_stat cpu_show_hist (FILE *st, UNIT *uptr, int32 val, CONST void *desc)
 {
 int32 k, di, lnt;
 t_stat r;
-CONST char *cptr = (CONST char *) desc;
+char *cptr = (char *) desc;
 InstHistory *h;
 
 if (hst_lnt == 0)                                   /* enabled? */
diff --git a/sigma/sigma_defs.h b/sigma/sigma_defs.h
index db50f14b..e2f85d3b 100644
--- a/sigma/sigma_defs.h
+++ b/sigma/sigma_defs.h
@@ -34,10 +34,6 @@
 
 #include "sim_defs.h"                                   /* simulator defns */
 
-/* Rename of global PC variable to avoid namespace conflicts on some platforms */
-
-#define PC PC_Global
-
 #if defined(USE_INT64) || defined(USE_ADDR64)
 #error "Sigma 32b does not support 64b values!"
 #endif
diff --git a/sigma/sigma_doc.doc b/sigma/sigma_doc.doc
deleted file mode 100644
index 0cfb805c..00000000
Binary files a/sigma/sigma_doc.doc and /dev/null differ
diff --git a/sigma/sigma_dp.c b/sigma/sigma_dp.c
index 1a3a4187..e493e58c 100644
--- a/sigma/sigma_dp.c
+++ b/sigma/sigma_dp.c
@@ -261,7 +261,7 @@ typedef struct {
     uint32 tpos;                                        /* to position */
     } DP_SNSTAB;
 
-static char *dp_cname[] = {
+static const char *dp_cname[] = {
     "7240", "7270", "7260", "7275", "7265", "T3281"
     };
 
@@ -1113,7 +1113,7 @@ t_stat dp_ioerr (UNIT *uptr)
 uint32 cidx = uptr->UCTX;
 uint32 dva = dp_dib[cidx].dva;
 
-sim_perror ("DP I/O error");
+perror ("DP I/O error");
 clearerr (uptr->fileref);
 dp_ctx[cidx].dp_flags |= DPF_DPE;                       /* set DPE flag */
 chan_set_chf (dva, CHF_XMDE);
diff --git a/sigma/sigma_lp.c b/sigma/sigma_lp.c
index 9d96f9f0..6d579adc 100644
--- a/sigma/sigma_lp.c
+++ b/sigma/sigma_lp.c
@@ -356,7 +356,7 @@ if (skp && CHP (CH_TOF, lp_cct[lp_cctp]))               /* skip, TOF? */
         }
 uptr->pos = ftell (uptr->fileref);                      /* update position */
 if (ferror (uptr->fileref)) {                           /* error? */
-    sim_perror ("Line printer I/O error");
+    perror ("Line printer I/O error");
     clearerr (uptr->fileref);
     chan_set_chf (lp_dib.dva, CHF_XMDE);
     return SCPE_IOERR;
@@ -391,7 +391,7 @@ if ((lp_model == LP_7440) || lp_pass) {                 /* ready to print? */
     fputc (lp_inh? '\r': '\n', uptr->fileref);          /* cr or nl */
     uptr->pos = ftell (uptr->fileref);                  /* update position */
     if (ferror (uptr->fileref)) {                       /* error? */
-        sim_perror ("Line printer I/O error");
+        perror ("Line printer I/O error");
         clearerr (uptr->fileref);
         chan_set_chf (lp_dib.dva, CHF_XMDE);
         return SCPE_IOERR;
diff --git a/sigma/sigma_map.c b/sigma/sigma_map.c
index cbd72b42..450e8f6c 100644
--- a/sigma/sigma_map.c
+++ b/sigma/sigma_map.c
@@ -529,8 +529,7 @@ if (QCPU_S89)
             ((R[rn] & S89_SR1_MARG) >> S89_SR1_MAROFF);
         break;
     case 0xB:                                           /* read sr0, clr */
-        mem_sr0[memu] = mem_sr1[memu] = 0;
-        /* fall through */
+        mem_sr0[memu] = mem_sr1[memu] = 0;              /* fall through */
     case 0x8:                                           /* read sr0 */
         R[rn] = (wd & S89_SR0_RD) |
             (((1u << (chan_num + 1)) - 1) << (S89_SR0_V_PORTS - (chan_num + 1)));
@@ -559,8 +558,7 @@ else switch (CC) {                                      /* 5X0 */
         mmc_wlk[ppag | 1] = R[rn] & 0xF;
         break;
     case 0xC:                                           /* read sr0, clr */
-        mem_sr0[memu] = 0;                              /* clr */
-        /* fall through */
+        mem_sr0[memu] = 0;                              /* clr, fall through */
     case 0x8:                                           /* read sr0 */
         R[rn] = S5X0_SR0_FIXED | (wd & S5X0_SR0_RD) |
             (((1u << (chan_num + 1)) - 1) << (S5X0_SR0_V_PORTS - (chan_num + 1)));
diff --git a/sigma/sigma_mt.c b/sigma/sigma_mt.c
index df153f3c..5dfa33c1 100644
--- a/sigma/sigma_mt.c
+++ b/sigma/sigma_mt.c
@@ -477,8 +477,7 @@ switch (st) {
     case MTSE_FMT:                                      /* illegal fmt */
     case MTSE_UNATT:                                    /* not attached */
     case MTSE_WRP:                                      /* write protect */
-        chan_set_chf (mt_dib.dva, CHF_XMME);            /* set err */
-        /* fall through */
+        chan_set_chf (mt_dib.dva, CHF_XMME);            /* set err, fall through */
     case MTSE_OK:                                       /* no error */
         chan_uen (mt_dib.dva);                          /* uend */
         return SCPE_IERR;
@@ -647,4 +646,4 @@ if (!(uptr->flags & UNIT_ATTABLE))
 uptr->UST = 0;
 sim_cancel (uptr + MT_REW);
 return sim_tape_detach (uptr);
-}
+}
\ No newline at end of file
diff --git a/sigma/sigma_pt.c b/sigma/sigma_pt.c
index 9b6a6342..cbda3052 100644
--- a/sigma/sigma_pt.c
+++ b/sigma/sigma_pt.c
@@ -1,6 +1,6 @@
 /* sigma_pt.c: Sigma 7060 paper tape reader/punch
 
-   Copyright (c) 2007-2008, Robert M. Supnik
+   Copyright (c) 2007-2018, Robert M. Supnik
 
    Permission is hereby granted, free of charge, to any person obtaining a
    copy of this software and associated documentation files (the "Software"),
@@ -24,6 +24,8 @@
    in this Software without prior written authorization from Robert M Supnik.
 
    pt           7060 paper-tape reader/punch
+
+   02-Jun-2018  RMS     Defanged clang signed/unsigned whining (Mark Pizzolato)
 */
 
 #include "sigma_io_defs.h"
@@ -158,7 +160,7 @@ return 0;
 t_stat pt_svc (UNIT *uptr)
 {
 int32 c;
-uint32 cmd;
+uint32 uc, cmd;
 uint32 st;
 
 switch (pt_cmd) {                                       /* case on state */
@@ -186,7 +188,7 @@ switch (pt_cmd) {                                       /* case on state */
                 break;
                 }
             else {                                      /* real error */
-                sim_perror ("PTR I/O error");
+                perror ("PTR I/O error");
                 clearerr (uptr->fileref);
                 chan_set_chf (pt_dib.dva, CHF_XMDE);    /* data error */
                 return pt_chan_err (SCPE_IOERR);        /* force uend */
@@ -196,7 +198,7 @@ switch (pt_cmd) {                                       /* case on state */
         if (c != 0)                                     /* leader done? */
             ptr_nzc = 1;                                /* set flag */
         if ((pt_cmd == PTS_READI) || ptr_nzc) {
-            st = chan_WrMemB (pt_dib.dva, c);           /* write to memory */
+            st = chan_WrMemB (pt_dib.dva, ((uint32) c));/* write to memory */
             if (CHS_IFERR (st))                         /* channel error? */
                 return pt_chan_err (st);
             if (st == CHS_ZBC)                          /* bc == 0? */
@@ -208,11 +210,11 @@ switch (pt_cmd) {                                       /* case on state */
         sim_activate (uptr, pt_unit[PTP].wait);         /* continue thread */
         if ((pt_unit[PTP].flags & UNIT_ATT) == 0)       /* not attached? */
             return ptp_stopioe? SCPE_UNATT: SCPE_OK;
-        st = chan_RdMemB (pt_dib.dva, (uint32 *)&c);    /* read from channel */
+        st = chan_RdMemB (pt_dib.dva, &uc);             /* read from channel */
         if (CHS_IFERR (st))                             /* channel error? */
             return pt_chan_err (st);
-        if (putc (c, pt_unit[PTP].fileref) == EOF) {
-            sim_perror ("PTP I/O error");
+        if (putc (((int32) uc), pt_unit[PTP].fileref) == EOF) {
+            perror ("PTP I/O error");
             clearerr (pt_unit[PTP].fileref);
             chan_set_chf (pt_dib.dva, CHF_XMDE);        /* data error */
             return pt_chan_err (SCPE_IOERR);            /* force uend */
diff --git a/sigma/sigma_tt.c b/sigma/sigma_tt.c
index f595e02e..1c357d2a 100644
--- a/sigma/sigma_tt.c
+++ b/sigma/sigma_tt.c
@@ -1,6 +1,6 @@
 /* sigma_tt.c: Sigma 7012 console teletype
 
-   Copyright (c) 2007-2008, Robert M. Supnik
+   Copyright (c) 2007-2018, Robert M. Supnik
 
    Permission is hereby granted, free of charge, to any person obtaining a
    copy of this software and associated documentation files (the "Software"),
@@ -30,6 +30,8 @@
    CR           input, mapped to NEWLINE and echoes CR-LF
    ^H           input, mapped to EOM and not echoed
    HT           input or output, simulates tabbing with fixed 8 character stops
+
+   02-Jun-2018  RMS     Defanged clang signed/unsigned whining (Mark Pizzolato)
 */
 
 #include "sigma_io_defs.h"
@@ -214,8 +216,8 @@ return SCPE_OK;
 
 t_stat tto_svc (UNIT *uptr)
 {
-uint32 c, cmd;
-uint32 st;
+int32 c;
+uint32 uc, cmd, st;
 
 switch (tt_cmd) {                                       /* case on state */
 
@@ -231,10 +233,10 @@ switch (tt_cmd) {                                       /* case on state */
         break;
 
     case TTS_WRITE:                                     /* char output */
-        st = chan_RdMemB (tt_dib.dva, &c);              /* get char */
+        st = chan_RdMemB (tt_dib.dva, &uc);             /* get char */
         if (CHS_IFERR (st))                             /* channel error? */
             return tt_chan_err (st);
-        c = ebcdic_to_ascii[c & 0xFF];                  /* convert to ASCII */
+        c = ebcdic_to_ascii[uc & 0xFF];                 /* convert to ASCII */
         tto_echo (c);                                   /* echo character */
         sim_activate (uptr, uptr->wait);                /* continue thread */
         if (st == CHS_ZBC)                              /* st = zbc? */